Sagittal Balance Correction in Cervical Compressive Myelopathy: Is it Helpful?
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.329595
Source of Support: None, Conflict of Interest: None
Keywords: Cervical compressive myelopathy, cervical thoracic junctional transfacet fixation, posterior cervical fixation, sagittal balance.
Cervical cord compressive myelopathy (CCM) is characterized by spinal cord compression due to physiologic narrowing of the sagittal diameter of the spinal canal either due to congenital or degenerative changes in the cervical spine. Clinical features often include neck pain, weakness of limbs, and/or sensory changes with an insidious, progressive, or acute onset, usually after a trivial trauma. Nurick grades and Modified Japanese Orthopedic Associations Score are often used to assess prognosis postintervention in patients with CCM, whereas associated pain evaluation is often done using Denis pain score and score on visual analogue scale.
Among the various surgical fixation methods employed for CCM, posterior cervical fixation with lateral mass screws, first described by Roy-Camille et al. in 1979 is regarded as gold standard especially for the management of multilevel CCM. Most of the literature were mentioned that fusion rate after lateral mass screw and rod fixation were almost 99–100%.,, The aim of the present study was correlating sagittal balance correction and function outcome in patients of CCM. However, if the etiology of CCM is degenerative changes of cervical spine, a deteriorating sagittal balance of the cervical spine is often associated with worsening clinical symptoms. In fact, measuring the T1 slope angle, Cobs angle, neck tilt angle (NTA), thoracic inlet angle (TIA), and sagittal vertical axis (SVA) are all proven techniques of measuring sagittal balance. Perhaps correcting sagittal balance of cervical spine during the surgical fixation may improve postoperative outcome. However, the role of optimal sagittal balance in the postoperative period is largely unexplored in these patients.
Singrakhia, et al. recently suggested that in patients with multilevel cervical myelopathy, multilevel laminectomy with lateral mass screw is a safe technique than laminoplasty and uninstrumented laminectomy. In fact, the authors question the need for lateral mass screw at each segment to ensure neurological and sagittal outcome.
In the current observational study, we evaluate the role of cervical thoracic junction fixation (transfacet C7-T1) in laminectomy and posterior fixation in patients with CCM. We investigate that if this surgical fixation of C7-T1 transfacet it improves postoperative sagittal balance and surgical outcome over short-term and long-term follow-up.
One hundred and two consecutive patients diagnosed of CCM who underwent cervical laminectomy between January 2015 and December 2019, formed the study population. The study was done at a tertiary referral centre in South India, after institutional ethics committee approval was obtained. The study was approved by institutional ethics committee in June 2017 and an informed consent was obtained from all the patients. The inclusion criteria were – CCM with multilevel pathology (more than two levels), lordotic and straight spinal alignment, with definitive radiological features of cervical cord compression, as diagnosed by an experienced radiologist., Patients with kyphotic cervical curvature and failure to obtain informed consent formed the exclusion criteria.
Data were collected at baseline (preoperatively), 3 months and 2 years postsurgery. The study variables included: demographics, preoperative neurological assessment, duration and severity of symptoms, neurological status. The primary outcomes of the study pain as measured by Denis pain score and neurological status measured by modified Japanese orthopedic association score (MJOS). Additional outcome measures included sagittal balance measured as the T1 slope using a computed tomography (CT) scan of cervical spine, demonstrated in [Figure 1]. a) T1 slope: the angle between an upper end plate of T1 and horizontal line. b) NTA: the angle formed by a vertical line of sternum tip and the line drawn in the center of upper end plate of T1. c) Cobb's angle C2-7: the angel between the horizontal line of C2 lower end plate and the horizontal line of C7 lower end plate. d) SVA C2-7: the distance between the plumb line of C2 dens tip and the plumb line of the center of C7 upper end plate. TIA: sum of the T1 slope and NTA.
All patients were operated under general anesthesia with necessary precautions taken of cervical spine during intubation. The patient was positioned in prone lying with head fixed by Sugita frame and pins with neutral position and maintaining physiological lordosis, which was confirmed with fluoroscopy guidance during head fixation. Exposure of the cervical spine level (C2–C7) done by midline skin incision and subperiosteal muscle elevation. The lateral mass screws (14 mm) and transfacet screws at C7-T1 (16 mm) were initially drilled and placement of crews were done at alternate level. During the surgery, the lowest level of screw placement in Group A patients was either at C5 or C6 lateral mass. In group B patients, the lowest level of screw placement was at C7-T1 junction, which involved transfacet screw placement and fixation [Figure 2]. On the contrary, intraoperatively, position of each screw position was assessed separately by fluoroscopy imaging guidance. Bending of rods was done according to the curvature of cervical spine before fixation with screw heads, followed by laminectomy. Postoperatively, patients in both the groups were advised to use a soft cervical collar for 6 weeks. One week after surgery, all the patients were advised neck exercises. CT of cervical spine was done on the postoperative period. Any intraoperative or postoperative complications were noted.
All continuous variables are expressed as mean ± standard deviation. Categorical variables are expressed as percentages. For short-term (3 month) follow-up, the study population of 102 patients was divided into two groups – Group A: patients underwent cervical laminectomy and lateral mass fixation without junction fixation, Group B: patients undergoing cervical laminectomy and lateral mass fixation including C7-T1 transfacet junction fixation.
At 2 years, while three (2.9%) patients were lost for follow-up, two (1.9%) patients died for reasons not associated with surgery and hence were excluded for long-term data analysis. Long-term data analysis was done in 53 (51.9%) patients (Group A: 26 and Group B: 27). Differences between groups for continuous variables were evaluated using independent Student t-test. Chi-square test was employed to evaluate differences between groups for categorical variables. All statistical analysis was done using statistical package for social sciences version 20.0 for windows, IBM Computers, New York, USA. A P ≤ 0.05 was considered to be significant.
The average age of the study population was 59.11 ± 12.05 years with 71 (69.6%) men. There were no significant differences between the groups for age and gender distribution [Table 1]. On comparison for presenting complaints, there were no significant differences between the groups for presenting complaints. Complications in the immediate postoperative period were not significantly different between groups; however, patients in group B had lesser length of postsurgical hospital stay (7.57 ± 6.61 vs 5.55 ± 1.81; P = 0.018) [Table 1]. Similarly, at admission, there was no significant difference between groups for total MJOS score [Table 2].
Short-term (3 months) follow-up
At 3 months after discharge, patients in group B had higher motor power of upper limb (3.64 ± 1.91 vs 4.47 ± 0.57; P < 0.001) and lower limbs (5.07 ± 1.72 vs 5.92 ± 1.13; P = 0.005). Furthermore, patients in group B had higher total MJOS score than Group A (13.68 ± 3.42 vs 15.51 ± 1.87; P = 0.001) [Table 2]. On the contrary, both the groups did not differ for score on pain rating scale, sensory symptoms, sphincter function either at baseline or at 3 months follow-up [Table 2]. In group A, a preoperative average T1 slope was 27.96 ± 5.45 and a postoperative it was 26.93 ± 8.73, with mean reduction of 1.04 ± 2.47. In group B, a preoperative T1 slope was 30.65 ± 8.44 and a postoperative was 17.60 ± 4.97, with mean reduction of 12.23 ± 9.53. Reduction of the T1 slope was statistically significant in group B as compare to group A (P value <0.001) [Table 2].
Two patients in group A and three patients in group B, respectively, had postoperative soakage of dressing with superficial serous discharge, which was managed with overstitch and antibiotics. One patient in each group had postoperative transient mild weakness of bilateral upper limbs, which was improved during the subsequent follow-up. In the present study, we did not came across any implant failure.
Long-term (2 year) follow-up
In the subset of 53 patients followed for 2 years to know long-term functional outcome. Findings reported in 3 months follow-up were consistent in long-term follow-up too [Table 3]. At 2 years, patients in group B had a better upper limb motor function (3.77 ± 1.14 vs 4.44 ± 0.50; P = 0.021), and total MJOS score (13.85 ± 3.49 vs. 15.37 ± 1.86; P < 0.052) than group A [Table 3].
In the current study, we evaluated the both short-term and long-term outcomes of patients with CCM at multiple segments who underwent routine laminectomy and posterior fixation in comparison to laminectomy and posterior fixation with additional C7-T1 junctional transfacet fixation. All the patients underwent lateral mass screw fixation at alternate levels than routine each level. We report that in patients with multisegment CCM undergoing surgical management, an additional C7-T1 junctional transfacet fixation improves long-term stability in sagittal plane. Moreover, these patients had better symptomatic relief than patients, where additional C7-T1 posterior fixation was not done.
The mean age and gender distribution and presenting complaints reported in the current study are similar to that reported by Watter et al. and O'laorie et al. It is now well known that each regional spine level keeps balance against the global axis of gravity with spinal curvature and imbalance of the spine in the sagittal plane is an important determinant of clinical symptoms, degenerative changes, and therefore postoperative recovery. Sagittal balance in cervical spine is as important as the more established pelvic incidence and lumbar lordosis. In fact, Jun HS et al. suggested the T1 slope was high in symptomatic compressive myelopathy patients compared to asymptomatic group patients. The results of the current study show that correction of this disturbed sagittal balance, by fixation of the C7-T1 level and improve the T1 slope, help improve both short-term and long-term postoperative outcomes than traditional laminectomy with posterior fixation [Figure 5]. Furthermore, in group B of our study, sagittal balance parameters calculated postoperatively showed and average NTA of 61.04°, TIA of 79.69°, and Cobb's angle of 11.14°, whereas the sagittal vertebral axis was 7–18 mm. Our observations are in cohesion with the existing literature.,
Since it is well established that the sagittal balance of cervical spine changes with increasing age and deteriorating clinical symptoms, deformity correction of cervical spine by correcting altered sagittal balance was achieved in the present study by correction of the T1 slope. The patient was positioned in prone with head fixed by Sugita frame and pins with neutral position to maintaining physiological lordosis, which was confirmed with fluoroscopy guidance during head fixation. Alignment was maintained during the whole surgery. Rods were bend according to the curvature of cervical spine before fixation to screws heads. We opted for transfacet screw fixation at the C7-T1 level because of greater pull-out resistance of transfacet screw placement than lateral mass fixation. At the rest of the involved spine segments, we opted for placements of screws at alternate levels followed by rod fixation as suggested by Singrakhia, et al., to avoid surgical complications and thus making the technique cost-effective.
Both at 3 months follow-up and long-term follow-up, although both the groups reported a significant pain reduction, the difference was not statistically significant. However, a lower length of stay in hospital, observed in Group B, is perhaps due to lower pain in the immediate postoperative period. However, the T1-slope/sagittal balance correction may not influence pain but only other symptoms. Further research on the role of C7-T1 fixation on various clinical variables will be beneficial. Importantly, in short term, better neurological outcome, measured by MJOS scores, in patients where fixation of the C7-T1 level is encouraging. This better outcome may be attributed to the concomitant, significant improvements observed in the T1 slope in these patients (with fixation of C7-T1 segment). In fact the postoperative T1 slope (19.48 ± 4.31) achieved with C7-T1 fixation is similar to the T1 slope of 23.16° reported in asymptomatic patients, of similar age group quoted in JH Park, et al. and Midde AK et al.,
Strengths and limitations
The current study is a single center, single surgeon experience; although this ensures consistency in surgical techniques, future research could validate our findings in large population, probably with robust randomization of patients. In the current study, we could not isolate the role of placements of screws at alternate levels followed by rod fixation, since the technique was used in patients in both the groups. The cost-effectiveness of the surgical technique (C7-T1 fixation and alternate level screw placement) over long term could also be investigated. The current study had multiple comparisons across various groups; our reported results, though clinically applicable, should be interpreted with caution.
In patients with multisegment CCM undergoing surgical management, an additional C7-T1 junctional transfacet fixation improves stability in sagittal plane that is sustained over long-term follow-up. This improved sagittal stability helps attain better symptomatic relief than patients where additional C7-T1 posterior fixation was not done. Moreover, lateral mass screw fixation may not be necessary at each level; this may reduce surgical complications and make the technique cost-effective.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3]